Volume 24, Issue 3, Pages 364-374 (March 2016) Structural and Functional Insights into the Evolution and Stress Adaptation of Type II Chaperonins  Jessica J. Chaston, Callum Smits, David Aragão, Andrew S.W. Wong, Bilal Ahsan, Sara Sandin, Sudheer K. Molugu, Sanjay K. Molugu, Ricardo A. Bernal, Daniela Stock, Alastair G. Stewart  Structure  Volume 24, Issue 3, Pages 364-374 (March 2016) DOI: 10.1016/j.str.2015.12.016 Copyright © 2016 Elsevier Ltd Terms and Conditions

Structure 2016 24, 364-374DOI: (10.1016/j.str.2015.12.016) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 1 Chaperonin Architecture Across Taxonomic Systems (A–C) Type I chaperonins (GroEL, HSP60, cpn60) consist of 14 copies of the same 60-kDa subunit arranged in a cylindrical particle with two seven-membered rings arranged back to back (A). Type II chaperonins (archaea, thermosomes; eukaryotic cytosol, CCT) generally consist of two eight-membered rings; thermosomes typically have two evolutionary-related (paralogous) subunits that are arranged alternately within one ring (B), eukaryotic CCT/TRiC has eight paralogous subunits per ring (C). (D–F) Sulfolobales have three paralogous subunits that, as we show here, can form three types of complexes: two species of nine-membered rings (either homomeric all-β or heterotrimeric αβγ) arranged in pairs to form octadecameric complexes (D and F), or hexadecameric αβ complexes (E). Structure 2016 24, 364-374DOI: (10.1016/j.str.2015.12.016) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 2 S. solfataricus TF55 All-β Chaperonin Structure (A) Cartoon representation of the biological unit. β subunits are shown in blue and nucleotides in yellow. (B) Cartoon representation of an individual β subunit with domains labeled: SL, sensor loop; Ct, C terminus. See also Figures S1, S2, S3, S7, and Table S1. Structure 2016 24, 364-374DOI: (10.1016/j.str.2015.12.016) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 3 S. solfataricus TF55 αβ Chaperonin Crystal Structures (A and B) Cartoon representation of the biological unit of the αβlongC (A) and αβshortC (B) hexadecameric structures. β subunits are shown in blue, α subunits in green and nucleotide in yellow. (C and D) Silhouette of individual subunits with respect to the closed hexadecameric structure (PDB: 1A6D, darker gray) and open hexadecameric structure (PDB: 3IZH, lighter gray). The subunits were superposed to the biological complex (Figure S4B), rather than individual subunits (Figure S4A), so that the relative position within the complex as well as conformational changes can be assessed. See also Figures S3, S6, S7, and Table S1. Structure 2016 24, 364-374DOI: (10.1016/j.str.2015.12.016) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 4 Crystal Contacts between the α Subunits of the αβshortC Crystal Structure (A and B) Silhouettes of the α subunits show how the different contacts cause a large change in the c axis dimension between the αβlongC (A) and the αβlongC (B). (C) Cartoon representation of the major crystal contact of the αβshortC structure; the helical protrusion (HP) has been partially unwound into a β-strand to extend the β-sheet formed by the sensor loop (SL) and the C terminus (Ct) of α and β subunits of an adjacent complex. See also Movie S1. Structure 2016 24, 364-374DOI: (10.1016/j.str.2015.12.016) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 5 Cryo-EM Reconstruction of the αβγ Complex (A) 3D reconstruction of the recombinant αβγ complex to 16-Å resolution in side and top views (gray density). One set of three symmetry-unrelated subunits (labeled 1,2,3) is highlighted in a red box. (B) Rigid body docking of the symmetrical all-β 18-mer structure into the EM density. The α and β equivalent subunits are colored light or dark cyan (indicating they cannot be assigned) and the γ subunit across the 2-fold symmetry axes is colored in red. See also Figures S5. Structure 2016 24, 364-374DOI: (10.1016/j.str.2015.12.016) Copyright © 2016 Elsevier Ltd Terms and Conditions

Figure 6 Mercator Projections of Chaperonin Complexes (A–D) Planar projections (in analogy to Cong et al., 2012) highlight the differences in subunit arrangement within chaperonin complexes. (A) Thermosome (α, green and β, blue), (B) αβlongC (α, green and β, blue), (C) αβγ model (α/β, light/dark cyan; γ, red), and (D) CCT (α yellow; β, red; γ, white; δ, orange; ɛ, green; ζ, black; η, indigo; and θ, purple) (PDB: 4V94). Two-fold symmetry axes are indicated. Note the different locations within the T. acidophilum and S. solfataricus structures, causing the differences in subunit arrangement. Structure 2016 24, 364-374DOI: (10.1016/j.str.2015.12.016) Copyright © 2016 Elsevier Ltd Terms and Conditions